7,158 research outputs found
Use of the supercritical fluid technology for the preparation of nanostructured hybrid materials and design of the interface
Premi extraordinari doctorat curs 2009-2010, àmbit d’Enginyeria IndustrialLos materiales compuestos nanoestructurados son considerados una opción prometedora
para la concepción de materiales multifuncionales. Sin embargo, la falta habitual de interacción
entre los componentes orgánicos e inorgánicos en los materiales híbridos nanoestructurados
comporta unas propiedades macroscópicas anisotrópicas que limitan su uso. Por ello, se hace
necesario el diseño de la interfase formada entre los componentes mencionados a fin de mejorar
sus prestaciones. En esta Tesis Doctoral se ha optado por el uso de dióxido de carbono supercrítico
(scCO2) para la modificación superficial de nanopartículas inorgánicas y para la preparación de
materiales híbridos nanoestructurados. Estos procesos supercríticos, diseñados como sostenibles,
se proponen como sustitutos de técnicas convencionales que empleen disolventes orgánicos.
El tratamiento superficial de nanopartículas de dióxido de titanio (TiO2) con
octiltrietoxisilano se ha empleado como sistema de estudio para evaluar el uso de recubrimientos
de alcoxisilanos bifuncionales como promotores de adhesión de partículas inorgánicas
nanométricas. El scCO2 se emplea como disolvente del alcoxisilano para la silanización del TiO2.
También se han llevado a cabo estudios fundamentales de solubilidad de octiltrietoxisilano en
CO2 y de la cinética del proceso de silanización del TiO2. La modulación de las propiedades
fisicoquímicas del scCO2 con la presión y la temperatura permite el control de las características
del recubrimiento con silano. El proceso de silanización supercrítico se ha extendido a diferentes
sistemas alcoxisilano-nanopartículas inorgánicas.
Asimismo, se ha evaluado la tecnología de scCO2 para la preparación de materiales
híbridos nanoestructurados que contengan nanopartículas inorgánicas silanizadas. El tratamiento
superficial de las nanopartículas favorece la distribución homogénea de éstas en el material
híbrido y mejora la interacción relleno-matriz orgánica. Se han procesado matrices
biopoliméricas de interés en ingeniería tisular, compuestas de ácido poliláctico o la mezcla
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polimetilmetacrilato/policaprolactona, con adiciones de nanopartículas de TiO2 o hidroxiapatita,
respectivamente. Para su procesado, se ha empleado scCO2 como no-disolvente utilizando la
técnica Particles from a Compressed Anti-Solvent (PCA). Además, se han preparado partículas
híbridas formadas por una mezcla lipídica de aceite de ricino hidrogenado y glicerilmonoestearato
con adiciones de TiO2 y cafeína, con posibles aplicaciones en cremas para uso tópico. Estas
partículas sólidas lipídicas se han obtenido usando la técnica Particles from Gas Saturated
Solutions (PGSS) que emplea scCO2 como soluto.
Por último, el proceso de silanización supercrítico se ha ensayado para materiales híbridos
complejos multiescalados. Se han procesado materiales de base cemento empleando un proceso
supercrítico de carbonatación-silanización en dos etapas. Primero, el cemento se carbonata de
manera acelerada usando scCO2 como agente de carbonatación. Este cemento, ya carbonatado, se
somete, finalmente, a un tratamiento hidrofóbico mediante silanización supercrítica, para su
posible aplicación en confinamiento de residuos peligrosos en ambientes húmedos o como
material de construcción duradero.Nowadays, society is asking for a global changing in the way of manufacturing goods in a
more sustainable manner. Indeed, the weight of the classical factors (cost, quality, appearance)
influencing the acceptance of a certain good in the market have currently changed.
Manufacturing requirements and regulations concerning environment protection (e.g., resource
consumption, sustainability, toxicity, CO2 footprint, recycling potential) and quality features (e.g.,
product guarantees, durability against aggressive environments, corporate vision) are aspects of
increasing concern. The competitive position of a company is influenced by seizing the
opportunities and challenges and by managing the risks that the changeable market has. As a
consequence, the industry is continuously looking for smart and innovative solutions for the
design and manufacturing of materials with novel properties and increased added value, and for
the production of materials already existing in the market in a more efficient manner.
Nanostructured hybrid composites have emerged as a promising class of innovative
materials for many industrial sectors (e.g., energy, optoelectronics, biomedicine, cosmetics). The
multicomponent composition of these materials provides them with unique properties arising
from the synergistic combination of the characteristics of their individual components structured
at the nanolevel. Nevertheless, in numerous hybrid materials, the lack of coupling or bonding
between the components often leads to anisotropic macroscopic properties, limiting their use.
Hence, the interaction at the interphase between hybrid components must be properly
engineered to enhance materials properties. In this PhD Thesis, the quest for sustainable and
environmentally friendly processes led to the use of supercritical carbon dioxide (scCO2) for both
the surface modification of nanometric inorganic particles and the preparation of nanostructured
hybrid materials. These processes are designed for the replacement of conventional methods
using organic solvents.
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Bifunctional alkoxysilane molecules, acting as adhesion promoters, are, herein,
investigated for the surface modification of nanometric inorganic particles. The surface treatment
of titanium dioxide (TiO2) nanoparticles with octyltriethoxysilane is taken as the model system
for study. In terms of processing, scCO2 is used as the solvent of choice for alkoxysilanes for the
surface modification of TiO2. Fundamental studies on the solubility of the used silane in CO2 in
the pressure range 8-18 MPa at two different temperatures (318 and 348 K) and on the kinetics of
the TiO2 silanization process are performed. For the scCO2-aided silanization process, studies are
conducted to ascertain the effects and interactions of the operating variables on the properties of
the final material. Results show that the tunable physicochemical properties of scCO2 with
pressure and temperature (e.g., density, solvation power) allows the engineering control of the
characteristics of the silane coating. Examples of the extension of the application of the
supercritical silanization process to other sets of alkoxysilanes and inorganic nanoparticles are
also presented.
The preparation of hybrid materials including silanized inorganic nanoparticles and
organic matrices is further tested using scCO2 technology. Surface treated nanoparticles are used
to facilitate the homogeneous distribution of the nanoparticles within the matix and to improve
the inorganic filler-organic matrix interaction. Biopolymeric matrices of either poly(L-lactic acid)
(L-PLA) or the blend poly(methylmethacrylate)/poly(ε-caprolactone) (PMMA/PCL) loaded with
nanometric titanium dioxide or hydroxyapatite, respectively, are prepared. To obtain these
hybrid materials, scCO2 is employed as an anti-solvent, using the Particles from a Compressed
Anti-Solvent (PCA) technique. Studies are performed to pursue the effect of the processing
conditions on the morphology of the precipitated hybrid materials. The resulting material,
obtained in the form of fibers, has suitable properties for its potential application in tissue
engineering. In a different system, hybrid particles composed of a lipidic matrix (hydrogenated
castor oil/glyceryl monostearate) loaded with silanized titanium dioxide and caffeine are
prepared. The Particles from Gas Saturated Solutions (PGSS) technique, assisted by the use of
scCO2 as a solute, is employed for the production of these solid lipid particles. The obtained
hybrid material is evaluated concerning the drug carrier and release ability and the UV-shielding
capacity. The UV-light protection and photoaging prevention capacity of the lipid-based hybrid
material provide excellent properties for the use of these particles in the formulation of
sunscreens and pharmaceutical dermal products.
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Finally, the possibility of extending the supercritical silane treatment to multiscale
complex hybrid materials is assessed. The technology based on the use of scCO2 is presented for
the two-step carbonation-silanization process of cement-based materials. In the first step, the
carbonation of cement is accelerated using scCO2 as the carbonation agent. The effects of the
cement formulation and process operation conditions on the microstructure and physicochemical
properties of carbonated samples are evaluated. The carbonation process is followed by the
hydrophobic treatment of the carbonated samples using a supercritical silanization method. The
surface modification of carbonated cement with octyltriethoxysilane confers water repellence to
the material. The carbonation-silanization process is scheduled and integrated to mitigate the
consumption of raw materials and the use of facilities.Award-winningPostprint (published version
Phytochemical Assessment of Native Ecuadorian Peppers (Capsicum spp.) and Correlation Analysis to Fruit Phenomics
[Abstract] In this work, the impact of pepper (Capsicum spp.) fruits morphology on their composition for health-promoting compounds was investigated. For that purpose, pepper accessions from Ecuador, one of the hotspots in Capsicum’s origin, were analyzed for ascorbic acid, polyphenols, capsaicinoids, and prevention of cholesterol oxidation. Plant and fruit phenomics were assessed with conventional descriptors and Tomato Analyzer digital traits. Significant differences among accessions and species revealed a large diversity within the collection. The Capsicum frutescens group displayed the highest levels of capsaicinoids, whereas the polyphenols shortly varied among the five domesticated species. Capsicum pubescens exhibited the lowest content of ascorbic acid. The conventional descriptors describing the magnitude of plants and fruits, as well as digital attributes under the categories of size, shape index, and latitudinal section, mostly explained the variance among Capsicum groups. Correlation test revealed that phytochemical components were negatively correlated with the morphometric fruit attributes, suggesting that huge fruits contained lower amounts of nutraceutical compounds. Multivariate analysis showed that parameters related to fruit size, shape, and nutraceutical composition primarily contribute to the arrangement of pepper accessions. Such results suggested that those traits have been subjected to higher selection pressures imposed by humans.Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria; RTA2015-00042-C02-02Xunta de Galicia; ED431C 2018/5
Fatal dual infection of avian polyomavirus and psittacine beak and feather disease virus in Chile
oai:ojs2.ajvs.cl:article/1A 6 week old Plum-headed parakeet (Psittacula cyanocephala) from a private bird collection in the Metropolitan Region of Chile died after presenting depression, ataxia, tremors of the head, subcutaneous hemorrhage and delayed crop emptying. Histological examination of liver tissue revealed intranuclear viral inclusion bodies and focal necrosis. Liver tissues and blood contained both avian polyomavirus (APV) and psittacine beak and feather disease (PBFD) viral nucleic acids (DNA), indicating dual viral infection. The purpose of this report is to describe the first case of concurrent psittacine beak and feather disease virus PBFDV and APV infection in a psittacine bird in captivity in Chile. PBFDV has not been reported until now in Chile
VLT/SPHERE robust astrometry of the HR8799 planets at milliarcsecond-level accuracy Orbital architecture analysis with PyAstrOFit
HR8799 is orbited by at least four giant planets, making it a prime target
for the recently commissioned Spectro-Polarimetric High-contrast Exoplanet
REsearch (VLT/SPHERE). As such, it was observed on five consecutive nights
during the SPHERE science verification in December 2014. We aim to take full
advantage of the SPHERE capabilities to derive accurate astrometric
measurements based on H-band images acquired with the Infra-Red Dual-band
Imaging and Spectroscopy (IRDIS) subsystem, and to explore the ultimate
astrometric performance of SPHERE in this observing mode. We also aim to
present a detailed analysis of the orbital parameters for the four planets. We
report the astrometric positions for epoch 2014.93 with an accuracy down to 2.0
mas, mainly limited by the astrometric calibration of IRDIS. For each planet,
we derive the posterior probability density functions for the six Keplerian
elements and identify sets of highly probable orbits. For planet d, there is
clear evidence for nonzero eccentricity (), without completely
excluding solutions with smaller eccentricities. The three other planets are
consistent with circular orbits, although their probability distributions
spread beyond , and show a peak at for planet e. The
four planets have consistent inclinations of about with respect to the
sky plane, but the confidence intervals for the longitude of ascending node are
disjoint for planets b and c, and we find tentative evidence for
non-coplanarity between planets b and c at the level.Comment: 23 pages, 14 figure
Maximum gravitational recoil
Recent calculations of gravitational radiation recoil generated during
black-hole binary mergers have reopened the possibility that a merged binary
can be ejected even from the nucleus of a massive host galaxy. Here we report
the first systematic study of gravitational recoil of equal-mass binaries with
equal, but anti-aligned, spins parallel to the orbital plane. Such an
orientation of the spins is expected to maximize the recoil. We find that
recoil velocity (which is perpendicular to the orbital plane) varies
sinusoidally with the angle that the initial spin directions make with the
initial linear momenta of each hole and scales up to a maximum of ~4000 km/s
for maximally-rotating holes. Our results show that the amplitude of the recoil
velocity can depend sensitively on spin orientations of the black holes prior
to merger.Comment: 4 pages, 4 figs, revtex
Globular Clusters: DNA of Early-Type galaxies?
This paper explores if the mean properties of Early-Type Galaxies (ETG) can
be reconstructed from "genetic" information stored in their GCs (i.e., in their
chemical abundances, spatial distributions and ages). This approach implies
that the formation of each globular occurs in very massive stellar
environments, as suggested by some models that aim at explaining the presence
of multi-populations in these systems. The assumption that the relative number
of globular clusters to diffuse stellar mass depends exponentially on chemical
abundance, [Z/H], and the presence of two dominant GC sub-populations blue and
red, allows the mapping of low metallicity halos and of higher metallicity (and
more heterogeneous) bulges. In particular, the masses of the low-metallicity
halos seem to scale up with dark matter mass through a constant. We also find a
dependence of the globular cluster formation efficiency with the mean projected
stellar mass density of the galaxies within their effective radii. The analysis
is based on a selected sub-sample of galaxies observed within the ACS Virgo
Cluster Survey of the {\it Hubble Space Telescope}. These systems were grouped,
according to their absolute magnitudes, in order to define composite fiducial
galaxies and look for a quantitative connection with their (also composite)
globular clusters systems. The results strengthen the idea that globular
clusters are good quantitative tracers of both baryonic and dark matter in
ETGs.Comment: 20 pages, 28 figures and 5 table
Identifying past social-ecological thresholds to understand long-term temporal dynamics in Spain
A thorough understanding of long-term temporal social-ecological dynamics at the national scale helps to explain the current condition of a country’s ecosystems and to support environmental policies to tackle future sustainability challenges. We aimed to develop a methodological approach to understand past long-term (1960-2010) social-ecological dynamics in Spain. First, we developed a methodical framework that allowed us to explore complex social-ecological dynamics among biodiversity, ecosystem services, human well-being, drivers of change, and institutional responses. Second, we compiled 21 long-term, national-scale indicators and analyzed their temporal relationships through a redundancy analysis. Third, we used a Bayesian change point analysis to detect evidence of past social-ecological thresholds and historical time periods. Our results revealed that Spain has passed through four socialecological thresholds that define five different time periods of nature and society relationships. Finally, we discussed how the proposed methodological approach helps to reinterpret national-level ecosystem indicators through a new conceptual lens to develop a more systems-based way of understanding long-term social-ecological patterns and dynamicsThis work was supported by the Biodiversity Foundation (http://www.fundacion-biodiversidad.es/) of the Spanish Ministry of Agriculture, Food and Environment. Partial
financial support was also provided by the Ministry of Economy and Competitiveness of Spain (project CGL2014-53782-P: ECOGRADIENTES). The Spanish National Institute for
Agriculture and Food Research and Technology (INIA) funded Marina García-Llorente as part of the European Social Fund. Blanca González García-Mon participated in this article as a “la
Caixa” Banking Foundation scholar. The funders had no role in the study design, data collection and analysis, preparation of the report, or the decision to submit the study for publicatio
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